For cellular communication, a User Equipment (UE) located in a cell accesses an eNodeB (eNB), receives control information for data communication from the eNB, and then transmits and receives data to and from the eNB. That is, since a UE performs data communication via an eNB, to transmit data to another cellular UE, the UE transmits the data to the eNB and the eNB receives the data and transmits the received data to the other UE. Since a UE can transmit data to another UE only via an eNB as described above, the eNB schedules a channel and a resource for data communication and transmits channel and resource scheduling information to each UE. Although each UE needs to receive allocation of the channel and the resource for data communication from the eNB for the above-described type of communication between the UEs via the eNB, Device to Device (D2D) communication has a structure in which a UE directly transmits and receives a signal to and from a desired UE without going via an eNB or a relay.
When D2D communication for direct data communication between UEs is performed by sharing a resource with a legacy cellular network, each UE can perform D2D communication after a D2D resource is allocated.
Furthermore, a control signal for D2D communication needs to be transmitted and received between the UEs. Accordingly, each UE should transmit D2D control information to a peer UE, and the peer UE may receive D2D data based on received D2D control information.